A growing number of diseases, including neuropathology and developmental disorders, are thought to result from disrupted transport of organelles. Melanosome transport in pigment cells is an ideal model system for studying the molecular mechanisms of organelle transport. We propose to examine the regulation of molecular motor proteins by applying genetics to the problem of melanosome transport in zebrafish melanophores. This will be accomplished by participating in two on going mutagenesis screens and screening zebrafish mutants specifically for alterations in melanosome dynamics. Mutants of interest will then be further examined by isolating their melanophores and, via live cell imaging, characterizing their defects in pigment transport through an assay system we have developed. Once we have identified mutants that are defective in microtubule pigment transport we will clone the genes responsible and examine their role in regulating motor activity.